back fire

Discussion in 'Propulsion' started by diversion, Jul 23, 2004.

  1. diversion
    Joined: Jul 2004
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    Location: MICHIGAN

    diversion New Member

    hi i have trojan f26 318 engine it back fires at around 2800 rpms sometime can't get to full rpm i change gas filters plug & wires what could it be
     
    diversion, Jul 23, 2004
    #1
  2. woodboat
    Joined: Nov 2003
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    Location: Baltimore MD, USA

    woodboat Senior Member

    On a Chrysler marine my first thought is the Ballast resistor. They are cheap and easy to replace. I thought I had a Carb issue on my last boat, A marinette with a 360 but it was only the resistor. Short of that I would be thinking coil and distributor. My current boat with a 350 chevy was backfiring. Replaced the distributor with a Mallory unilite, all is well now.
     
    woodboat, Jul 26, 2004
    #2
  3. Corpus Skipper
    Joined: Oct 2003
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    Location: Corpus Christi TX

    Corpus Skipper Hopeless Boataholic

    I concur with woodie. You can eliminate a lot of headaches with electronic ignition. I converted my 350s with a kit from Pertronics, replaces the points, uses same distributor. About $70 per engine, available from Summit Racing (www.summitracing.com). They're worth their weight in gold! :D Also got easier starting and reduced fuel consumption (3 gph per with new carbs as well)
     
    Corpus Skipper, Jul 29, 2004
    #3
  4. Corpus Skipper
    Joined: Oct 2003
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    Corpus Skipper Hopeless Boataholic

    Corpus Skipper, Jul 29, 2004
    #4
  5. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    2800 RPM is about when the secondary springs start stretching. If your distributor shaft/bushing is worn out or the springs are weak it will overadvance.
     
    gonzo, Jul 31, 2004
    #5
  6. trouty

    trouty Guest

    Look inside

    the distributor cap, and make sure there isn't an blackened carbon 'arc' created between two adjacent HT outlet poles on the inside of the cap.

    If it gets wet under the cap and any salt deposits there - the spark can track across to an adjacent spark plug wire lead inside the dizzy cap - thus firing a cylinder before the exhaust valve is closed - (or when the inlet valve is still open - meaning a backfire thru the carby!).

    Good luck.
     
    trouty, Jul 31, 2004
    #6

  8. Frans X L
    Joined: Jun 2004
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    Location: Cape Town, South Africa

    Frans X L Junior Member

    backfiring is usually a sign of retarded ignition timing.
     
    Frans X L, Aug 1, 2004
    #7
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